feat(ux): per-view subtitles, correspondence cross-links, mobile kanban, a11y

Continuing the product/UX review's deferred items:

- Every top-level view now gets a one-line subtitle under its title
  (Dashboard/Jobs/Kanban/Reminders/Correspondence/Gmail review) stating
  what that specific view is for, instead of navigation being the only
  signal of what each page does.
- Correspondence inbox and Gmail review queue cross-link to each other
  instead of being two unexplained flat sidebar items -- kept both nav
  entries (renaming/nesting risked breaking muscle memory) but made the
  relationship between them explicit in the UI itself.
- Kanban board switches to a horizontal scroll-snap row on phone-width
  viewports instead of stacking all 5 columns vertically, which meant
  a lot of scrolling to see anything past "Applied".
- Match-score ring gets an aria-label with the actual percentage --
  it was two nested decorative CircularProgress elements with no
  accessible text. (Keyboard-accessible status changes on kanban cards
  were already covered by the existing "..." menu -- no gap there.)

job-tracker-ui/src/components/KanbanBoard.tsx

@@ -101,7 +101,18 @@ export default function KanbanBoard() {
       />
 
       {!jobsResource.loading && !jobsResource.error ? (
-        <Box sx={{ display: "grid", gridTemplateColumns: { xs: "1fr", md: "repeat(3, 1fr)", xl: "repeat(6, 1fr)" }, gap: 2, alignItems: "start" }}>
+        <Box
+          sx={{
+            display: { xs: "flex", md: "grid" },
+            gridTemplateColumns: { md: "repeat(3, 1fr)", xl: "repeat(6, 1fr)" },
+            gap: 2,
+            alignItems: "start",
+            overflowX: { xs: "auto", md: "visible" },
+            scrollSnapType: { xs: "x mandatory", md: "none" },
+            pb: { xs: 1, md: 0 },
+            "-webkit-overflow-scrolling": "touch",
+          }}
+        >
           {STATUSES.map((status) => {
             const c = toneColor(theme, status);
             const list = groups.get(status) ?? [];
@@ -114,6 +125,8 @@ export default function KanbanBoard() {
                   p: 1.5,
                   borderRadius: 3,
                   minHeight: 220,
+                  flex: { xs: "0 0 85vw", md: "none" },
+                  scrollSnapAlign: { xs: "start", md: "none" },
                   border: "1px solid",
                   borderColor: "divider",
                   background: theme.palette.mode === "dark" ? alpha(theme.palette.common.white, 0.02) : alpha(theme.palette.text.primary, 0.015),